Displays can be created from an array of light emitting devices each controlled by individual circuits (i.e., pixel circuits) having transistors for selectively controlling the circuits to be programmed with display information and to emit light according to the display information. Thin film transistors (“TFTs”) fabricated on a substrate can be incorporated into such displays. Displays including current-driven emissive devices may be operated by drive transistors in each pixel circuit connected in series with the emissive device to convey current through the emissive devices according to programming information. Storage capacitors may be included in each pixel circuit to receive a voltage based on the programming information and apply the voltage to the drive transistor. TFTs fabricated on poly-silicon tend to demonstrate non-uniform behavior across display panels and over time. Furthermore, emissive devices degrade over time and may require increasing applied voltage to maintain luminance levels, over time. Some displays therefore utilize compensation techniques to achieve image uniformity in TFT panels.
Compensated pixel circuits generally have shortcomings when pushing speed, pixel-pitch (“pixel density”), and uniformity to the limit, which leads to design trade-offs to balance competing demands amongst programming speed, pixel-pitch, and uniformity. For example, additional lines and transistors associated with each pixel circuit may allow for additional compensation leading to greater uniformity, yet undesirably decrease pixel density. In another example, programming speed may be increased by biasing or pre-charging each pixel circuit with a relatively high biasing current or initial charge, however, uniformity is enhanced by utilizing a relatively low biasing current or initial charge. Thus, a display designer is forced to make trade-offs between competing demands for programming speed, pixel-pitch, and uniformity.
Displays configured to display a video feed of moving images typically refresh the display at a regular frequency for each frame of the video feed being displayed. Displays incorporating an active matrix can allow individual pixel circuits to be programmed with display information during a program phase and then emit light according to the display information during an emission phase. The displays operate to program each pixel in the display during a timing budget based on the refresh rate of the display and the size of the display. The refresh rate of the display can also be influenced by the frame rate of the video stream.